(Color online) Schematic of the cryogen-free magnet: (A) room temperature bore, (B) radiation shield, (C) superconducting solenoid, (D) copper thermal links, (E) cryocooler, (F) protection terminals, and (G) magnet terminals.
(Color online) Photograph of the entire HF EPR setup at the NCSU installation site: (A) a cryogen-free magnet, (B) cryocooler, (C) aluminum support legs with rubberized pads sandwiched between the legs and the magnet, (D) aluminum cage that is mechanically insulated from the magnet (note that the height of the vertical beams is ), (E) movable platform with a millimeter-wave bridge for EPR experiments, (F) flow cryostat for variable temperature measurements that is supported by the cage and is therefore mechanically insulated from the magnet, and (G) cryostat support beams.
(Color online) Overall schematic of the cryogen-free magnet and auxiliary systems.
(Color online) Temperatures of different parts of the cryogen-free magnet system during a typical cool down after storing the system at room temperature.
(Color online) Temperatures of different parts of the cryogen-free magnet system during ramping the main coil from in magnetic field up to the maximally specified rate of of the full value.
(Color online) Temperatures of different parts of the cryogen-free magnet system during operating the magnet in persistent and nonpersistent modes at magnetic field of and with current in the leads. The current was stabilized by a Danfysik power supply. A nonpersistent state was achieved by maintaining the switch at with a heater.
Long-term stabilization of the magnetic field of the main coil in a nonpersistent state by the Danfysik power supply. Note that relative accuracy of the Metrolab PT 2025/00/4 gaussmeter employed for magnetic field measurements is approximately .
(Color online) Temperatures of different parts of the cryogen-free magnet system during quenching the main coil upon testing the magnet for the maximum attainable energization rate. Note that just after and after the quench the CFM system was ready again for operation.
Experimental ( band) EPR spectra from nitroxide radical Tempone (perdeuterated -tetramethyl-4-piperidone-1-nitroxide); single scans with time constant and magnetic field modulation amplitude. (A) A spectrum with the magnet actively cooled by a GM-cycle cryocooler and (B) A spectrum taken without active cooling and, thus, in the absence of any vibrations from the cryocooler.
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